Add individual assets to a portal in an asset section. Click Add Assets to add an asset section.
After the asset section is added, search for assets to add to the portal.
Add to Existing Portals
Add assets as often as you need to existing portals by clicking the Edit pencil icon. Search for assets to add, then click Update when you're done. You can also add a new asset section to the portal then search for assets to add to it.
Remove assets by clicking Edit pencil icon. Uncheck the ones you want to remove, then click Update.